/Engine/Plugins/Online/OnlineServices/Source/OnlineServicesInterface/Public/Online/Schema.h
The passed in accessor is an interface which must provide a definition for GetMutableClientSnapshot.
template<typename FSnapshotAccessor> class TSchemaCategoryInstance : public [UE::Online::Private::FSchemaCategoryInstanceBase](API\Plugins\OnlineServicesInterface\Online\FSchemaCategoryInstanceBase)